Sutureless Fixation of Amniotic Membrane Gregory T. Hofeldt, MD, removes a large pterygium and takes extra care to excise the root completely. The surgeon measures the defect with calipers to determine the size of the graft. He cuts an over-sized Ambio5 (IOP Inc.) graft, a dehydrated human amniotic membrane graft, and affixes it to the bare sclera.